1. Field of the Invention
This invention relates to a new antitumor substance and, in particular, relates to a new substance having antitumor activity against certain types of tumors and containing protein, which substance is obtained from an epidermal portion of rice.
2. Description of the Prior Art
It is known from Japanese Patent Provisional Publication (hereinafter, referred to as JPPP) 50(1975)--77518, that a substance called RBA, having a physiological activity, is obtained by extracting rice bran with a solvent. The substance RBA is a phytalbumin containing 15-20 mole % of cysteine and 23-26 mole % of glycine, and it has an isoelectric point in the range of pH 7-pH 10. This RBA can be obtained, for example, by extracting rice bran with an aqueous sodium chloride solution.
It is also known from JPPP 53(1978)--139713 that an antitumor substance is obtained from an epidermal portion of a seed, such as grain, treated with heating under pressure. The thus-obtained substance, however, is a nonproteinaceous high molecular weight substance and is supposed to be a higher fatty acid or analog thereof, as described in the above-identified JPPP.